1. Field of the Invention
The present invention generally relates to a mobile communication system and more particularly to a system and method of exchanging state information in a mobile communication system.
2. Background of the Related Art
Recent developments in mobile communication techniques have allowed mobile communication terminals to transmit and receive various types of multimedia such as images, mobile images, various types of data as well as voice. The terminals also provide users with services that allow a battery state or reception state to be checked through a display unit such as an LCD, make a phone call simply by searching a desired phone number through a late call list memory function or a phone number storing function, and check his/her current position with a global positioning system (GPS) function combined with the mobile terminal.
FIG. 1 illustrates a construction of a general mobile communication system, and FIG. 2 is a flow chart of a call processing operation performed in the mobile communication system.
As shown in FIG. 1, the mobile communication system includes mobile communication terminals 10a and 10b and a base station 20. The terminals perform voice call communication and a supplementary service by sending an originating call or receiving a terminating call while moving. The base station 20 processes the originating call transferred from the mobile communication terminals or transfers a terminating call requested from an external system to the mobile communication terminals, and also processes channel information together with the mobile communication terminals through a paging channel.
As shown in FIG. 2, a call processing operation of the mobile communication system is performed as follows. When power is applied to a mobile communication terminal, the terminal is initialized. In the initialization state, the terminal reads information required for its operation from an EEPROM and sets a parameter, and receives required system information through a pilot channel and a sync channel transmitted from the base station, putting it into an idle state. That is, in the initialization state, information required for the mobile communication terminal is set and the environment for transition to the idle state is set.
In idle state, the mobile communication terminal is maintained in a state that it can receive a system parameter through the sync channel or respond to various messages such as paging.
When a user makes a phone call with the mobile communication terminal, the terminal executes a system connection to the base station through an access channel and transfers an originating call.
In a traffic state, the base station processes the originating call received from the terminal and transfers a termination call to the mobile terminal of the other party, thereby making a call connection between the terminals. At this time, the mobile communication terminal displays a propagation strength on a display unit using an internal received signal strength indication (RSSI) function.
When the mobile communication terminal completes a specific operation in the system access state, it returns to the idle state or to the traffic state. If the mobile communication terminal fails to receive a paging channel in the idle state, it switches to the initialization state.
FIG. 3 is a flow chart of a process for performing call communication in the mobile communication system in accordance with the related art. When an originating call is generated from the originating side terminal 10a and transmitted to base station 20 (step S11), the base station receives the originating call, generates a terminating call, and transfers it to the receiving side terminal 10b. As the receiving side terminal 10b responds to the terminating call, the originating and receiving side terminals are connected for call (step S12). At this time, the display units of the originating and receiving side terminals display current state information, propagation strength, or the like.
When a user of the originating side terminal 10a or the receiving side terminal 10b presses ‘END’ or a call is not available because of a network failure, a communication release message is transferred to the base station 20 (step S13). Then, the base station 20 transfers the communication release message to the receiving side terminal 10b or to the originating side terminal 10a and the call connection state is released (step S14).
As the call connection is released, the originating and receiving side terminals return to the initialization state (step S15). Meanwhile, the user of the terminal which has been released in its call connection due to the network failure may attempt a call again.
The mobile communication system of the related art has at least the following problems.
First, the user of the originating side terminal can recognize the state of the originating side terminal but not the state of the receiving side terminal. Thus, if the receiving side terminal rejects a call of the originating side terminal, or if a network failure occurrence makes a call connection unavailable, the originating side terminal may repeatedly attempts a re-connection to the receiving side terminal. This degrades users' convenience.
More specifically, if a communication failure occurs, for example, because the user of the receiving side terminal has intentionally turned off his terminal, or because the receiving side terminal has been turned off as a result of a low-voltage condition of a battery, or because a propagation reception state of the receiving side terminal is so bad that a call is disconnected, the user of the originating side terminal, who does not know about the state of the receiving side terminal, may attempt a call connection repeatedly to no avail.
Second, after a call connection is released because of a network failure, when the user of the originating side terminal attempts re-connection to the receiving side terminal, the user must re-enter the entire key sequence (e.g., receiving terminal's telephone number) to transfer a recall signal, resulting in degradation of users' convenience.
Third, if the user of the originating side terminal keeps attempting re-connection to the receiving side terminal in a situation that a call connection cannot be made because of a network failure, not only is the battery power of the originating side terminal substantially consumed for generation of the originating call but also the base station must allocate a channel continuously for the attempted re-connecting. Thus, operation resources of the base station are also wasted.